Packing plant by-products, such as lungs, kidneys, hearts and other parts generally not consumed by humans of both beef and pork, are often sold and used to make pet food. These by-products are initially at the body temperature of the butchered animal when removed therefrom, and are therefore highly susceptible to spoilage. Due to such potential for spoilage, the by-products have a very short life. The warm by-products must be quickly transported from the packing plant which slaughters the animal to the remote processing plant for conversion into pet food. Without such hurried pick up and delivery, the by-products become spoiled and must be discarded.
Because such rush pick-up and delivery is rarely feasible, packing plants have had to use either cooler storage or dry ice to chill the product while a sufficient quantity to comprise a shipping load accumulates. To adequately chill such products in a walk-in cooler, it is necessary to hang the product on racks so as to immediately expose all surfaces to the chilled air. If the product freezes it has to be further processed or allowed to thaw before processing, making the control of the cooler temperature critical. Similarly, the use of dry ice entails boxing and careful monitoring in order to avoid freezing. Boxes used for this purpose are expensive and the cost of dry ice is roughly 35% to 40% of the value of the product. Losses due to inadvertent freezing is practically unavoidable.